Electrically controlled bolt locks are commonly used in many security applications. The flexibility provided by an electric lock assembly allows the opening and closing of the lock to be remotely controlled from a guard station to allow limited access to a facility.
Such electrically controlled locks are known from U.S. Pat. No. 4,799,719, which discloses a motor operated lock wherein the motor is translated when the motor shaft rotates, the motor shaft acting as the bolt of the lock and engaging or disengaging the door to lock or unlock the door. The motor is located on a fixed platform and is moved by the cooperation of a nut affixed to the platform and a threaded portion of the motor shaft. The assembly may be located inside or exterior to the wall and may be adapted for easy removal. The motor direction and travel limits are controlled by an appropriate electrical circuit. The described lock uses a motor to drive a deadbolt into and out of a door. The motor is actuated in a first direction to cause a rotation of the motor shaft, which is then converted into a linear, translational motion which is in turn transmitted to the bolt which is projected through the door jamb and into the door. The travel of the deadbolt into the door is discontinued on the signal of a feedback switch connected to an appropriate moving member to sense when the lock is fully closed. When the lock is desired to be opened, the motor is actuated to run in a reverse direction and to thereby withdraw the bolt from the door, into the door jamb and the wall. The withdrawal motion of the bolt is discontinued on the signal of a second feedback switch which senses when the bolt is sufficiently withdrawn to allow the door to be opened. The motor shaft contains a threaded portion which is connected to a nut having a fixed location to allow the motor to move transversely because the rotational motion of the shaft is converted to translational motion.
In sliding bolt locking devices, particularly in those intended for outdoor use, such as with gates or exterior doors, simplicity is a major advantage. Every moving element in the device may become stuck due to entrance of water or dirt, the formation of ice, corrosion, due to temperature differences or other weather related influences and/or misuse. It is therefore a recurring concern, when designing sliding devices to keep the technical solutions as simple as possible, with the smallest possible number of moving elements.
An important drawback of the electrically operated locking devices is that in case of an error in the activation system of the extended electrically controlled bolt the access through the passage remains blocked. There is thus no emergency opening possibility provided in case of an internal failure or an external power failure. Usually, in case of power failure, the locking device needs to be physically removed from the gate (closing member) it closes off in order to allow entrance, an operation which is time consuming and requires a relatively high skill level and specialised training, which is not necessarily widespread under emergency rescue personnel.
FR 2 592 911 describes an electrically controlled lock comprising an electric motor in a fixed frame, driving a bolt. Under normal operating circumstances, the lock is opened and closed through the movement of the bolt which is driven by the electric motor. However, this lock is also equipped with an alternative in case electrically unlocking is not possible. For this purpose, the lock disposes of two cylindrical and coaxial boreholes of different diameter where the motor (largest diameter) and the bolt are positioned. The motor cannot translate as it is fixed by a compressed spring on one side and a pin on the other side. This pin is installed for reasons of security, and it can be pulled out in case of an emergency. The immediate effect is that the spring decompresses and the motor is moved along its cylindrical borehole, moving the bolt with it to a position leaving the lock open.
However, this is not an ideal solution if the lock is manually accessible from both sides. This is the case in gates (panels, closing members), which are for example comprising bars. A person on the other side of the gate can have access to the pin and may therefore be able to open the gate at all times.
Furthermore, this is also not an ideal solution if the pin is removed on a regular base. In order to re-use the lock, the electric motor and the pin always need to be pushed back into their original position, against the force of the spring which is difficult and time consuming to execute.
There remains therefore a need for an electrically operated locking device which may be unlocked independently in case the electrical operation is not operable. It is also desirable that such unlocking possibility is only provided to dedicated personnel, such as personnel belonging to emergency services.
A particular situation is the locking and unlocking of rotationally opening gates. Remote controlled opening of hinged or sliding gates is commonly used. However, a lock for these gates will either be electrically powered, leaving the gates locked upon power failure, or manually unlocked, thus nullifying the effect of remote control.
There is therefore a particular need for an electric locking device which can be combined with the remote controlled opening of rotationally or sliding hinged gates. Furthermore, a person on the other side of the gate should not be able to open the lock, yet it should be easy to access and to be unlocked by emergency services or authorized persons on either side of the gate. Finally, the electric locking device should be resistant to vandalism.